1. Field of the Invention
The present invention relates to a procedure and device for drying a web, e.g., a paper or tissue web, in motion in a machine for producing or converting the web.
2. Discussion of Background Information
Guiding the web over rotating, heated cylinders for drying is known in the art. Heating the web in this manner releases moisture in the form of steam. As the dry content of the web increases, however, the capacity of the web to outwardly release steam from the inside decreases.
This evaporation can be intensified by guiding the web over vacuum guide rolls. Generally such guide rolls are composed of a perforated roll sleeve having a negative pressure created inside either directly, through connection with a negative pressure source, or indirectly, through suctioning or vacuuming of an area of the perforated roll sleeve that is not covered by the web.
In this manner, the negative pressure draws the steam out of the web. However, creating the requisite negative pressure, particularly at a high level, is associated with significant technical expense and expenditure of energy.